Strategies to improve protection against low-pathogenicity H7 avian influenza virus infection using DNA vaccines.

Eukaryotic expression plasmids encoding either the avian influenza hemagglutinin or matrix genes (pCMV-HA and pCMV-M, respectively) were constructed. The viral genes were derived from a low-pathogenicity H7N1 strain, A/Chicken/Italy/1067/99, isolated during the 1999-2001 epizootic in Italy. The plasmid was administered to 4-to-5-wk-old specific-pathogen-free chickens by several different injection methods. For the initial studies comparing methods of vaccine injection, results were compared based on hemagglutination inhibition (HI) response following immunization with pCMV-HA. Additional studies with coadministration of both pCMV-HA and pCMV-M was evaluated based on HI response and viral isolation after homologous challenge. Preliminary results indicate that a device intended to inject insulin in humans (Medijector) and the coadministration of both plasmids improved protection against H7 infection.